Lesson 8 Corrections to sextant observations

LESSON 1
LESSON 2
LESSON 3
LESSON 4
LESSON 5

LESSON 7
LESSON 8
LESSON 9

We now know how to reduce a sight, that is, to determine the exact altitude and azimuth a navigational body would have from a precise location on the surface of the Earth at a given moment in time.

Armed with that ability, we're all set to compare the altitude from an actual observation of a body with the altitude computed for that body at that time at a place nearby.

When we take observations of a body, there are several significant corrections which must be applied to the observations before they can be usefully compared to the computed value(s).  The errors and corrections are described fully in the Preview Summary

When we take a sight, the value read from the sextant is called the sextant altitude (hs). It is raw data in need of "correction."  Once we've made all the corrections, the resulting altitude is called the observed altitude (Ho); it is ready to be compared with the computed altitude (Hc). We'll talk more about that process in Lesson 9, Lines of Position.

 

Table of contents/Assignments